1. Field of Invention
This invention relates generally to systems and methods of eye tracking that enable a user to provide input to a computing device from a mobile position.
2. Discussion of Related Art
Eye tracking involves the measurement of the location of a point that falls within a direction of a gaze of an eye, i.e., where an eye is looking. For a number of eye tracking systems, a camera is mounted in an arrangement where the lens of the camera captures information regarding the position of a pupil of an eye. Images captured by the camera are analyzed and calibrations are made so as to provide a correlation between the image of the pupil of the eye and the direction of a gaze. In this respect, once the eye tracking system is calibrated, particular images of the pupil as captured by the camera will map to points in space at a location spaced from the person's eye.
When capturing images of the pupil, some eye tracking systems record images in the visible spectrum of light. However, when visible light is used in recording images of the eye, the occurrence of specular reflection may reduce accuracy. Therefore, eye tracking systems more frequently implement infrared imaging when recording images of the pupil so as to create a sharper contrast in the image between the pupil and the sclera portions of the eye.
Eye tracking can be useful for a number of applications. For example, people who are physically limited and unable to control a computer through usual movement (e.g., typing or moving a mouse with the hands) can use eye tracking systems to control a computer. An eye tracking system may involve a camera that is mounted adjacent to a monitor of a computer where a lens of the camera is directed toward an eye of the user who is positioned at a distance from the monitor. The camera uses infrared light to capture images of a pupil of an eye of the user. The head of the user must remain in a fixed position for the camera to capture video information of the user's eye. The location of the pupil of the eye captured from the camera is calibrated to a point on a screen of the monitor of the computer. When the system determines that the direction of the gaze of the eye falls on a screen of the monitor of the computer, the user is able to provide input to the computer by using certain actions of the eye. A typical control action may include moving a pointer displayed on the screen of the monitor by moving the direction of gaze of the eye around the screen. Another control action may be to blink the eye a particular number of times to select a particular object displayed on the screen. Looking at an object on the screen of the monitor for a predetermined period of time may also signify to the computer that the object at which one is looking is selected or highlighted. However, if the user physically moves to a different non-calibrated position relative to the screen, images of the eye recorded by the eye camera might no longer correspond accurately to points on the screen where the user is looking. Some systems attempt to deal with this problem by tracking the position of the face along with the eye, and correcting for the new position. In such systems that incorporate facial tracking along with eye tracking, the device captures a broad image of the user (i.e., the face and the eye), and as a result, the accuracy of such devices suffers, since the resolution of the captured images of the eye is reduced when the image captures a broader scene. The accuracy decreases even more as the position of the user's head moves farther away from the calibrated position.
Conventional eye tracking systems that involve methods for a user to control a computing device through movement of the eye are disclosed in U.S. Patent Publication No. 2009/0315827 entitled “Generation Of Graphical Feedback In A Computer System”; U.S. Patent Publication No. 200800284980 entitled “Eye Tracker Having An Extended Span Of Operating Distances”; U.S. Patent Publication No. 2009/0125849 entitled “Eye Tracker With Visual Feedback”; U.S. Patent Publication No. 2006/0109242 entitled “User Interface For Impaired Users”; U.S. Pat. No. 7,736,000 entitled “Method and Apparatus for Tracking Eye Movement”; U.S. Pat. No. 7,572,008 entitled “Method and Installation for Detecting and Following an eye and the Gaze Direction Thereof”; U.S. Pat. No. 6,637,883 entitled “Gaze Tracking System and Method”; U.S. Pat. No. 6,367,932 entitled “Apparatus And Method For Visual Field Testing”; U.S. Pat. No. 6,204,828 entitled “Integrated Gaze/Manual Cursor Positioning System”; U.S. Pat. No. 5,360,971 entitled “Apparatus And Method For Eye Tracking Interface”; and U.S. Pat. No. 4,950,069 entitled “Eye Movement Detector With Improved Calibration And Speed” all of which are incorporated herein by reference in their entirety.